TSWV Infection Research Articles

Tomato Spotted Wilt Virus Suppresses the Antiviral Response of the Insect Vector, Frankliniella occidentalis, by Elevating an Immunosuppressive C18 Oxylipin Level Using Its Virulent Factor, NSs.

Orthotospovirus tomatomaculae (tomato spotted wilt virus, TSWV) is transmitted by the western flower thrips, Frankliniella occidentalis. Epoxyoctadecamonoenoic acids (EpOMEs) function as immune-suppressive factors, particularly in insects infected by viral pathogens. These oxylipins are produced by cytochrome P450 monooxygenases (CYPs) and are degraded by soluble epoxide hydrolase (sEH). In this study, we tested the hypothesis that TSWV modulates the EpOME level in the thrips to suppress antiviral responses and enhance its replication. TSWV infection significantly elevated both 9,10-EpOME and 12,13-EpOME levels. Following TSWV infection, the larvae displayed apoptosis in the midgut along with the upregulated expression of four caspase genes. However, the addition of EpOME to the viral treatment notably reduced apoptosis and downregulated caspase gene expressions, which led to a marked increase in TSWV titers. The CYP and sEH genes of F. occidentalis were identified, and their expression manipulation using RNA interference (RNAi) treatments led to significant alternations in the insect's immune responses and TSWV viral titers. To ascertain which viral factor influences the host EpOME levels, specialized RNAi treatments targeting genes encoded by TSWV were administered to larvae infected with TSWV. These treatments demonstrated that NSS expression is pivotal in manipulating the genes involved in EpOME metabolism. These results indicate that NSs of TSWV are crucially linked with the elevation of host insect EpOME levels and play a key role in suppressing the antiviral responses of F. occidentalis.

Genome-Wide Identification and Functions against Tomato Spotted Wilt Tospovirus of PR-10 in Solanum lycopersicum.

Tomato spotted wilt virus impacts negatively on a wide range of economically important plants, especially tomatoes. When plants facing any pathogen attack or infection, increase the transcription level of plant genes that are produced pathogenesis-related (PR) proteins. The aim of this study is a genome-wide identification of PR-10 superfamily and comparative analysis of PR-10 and Sw-5b gene functions against tomato responses to biotic stress (TSWV) to systemic resistance in tomato. Forty-five candidate genes were identified, with a length of 64–210 amino acid residues and a molecular weight of 7.6–24.4 kDa. The PR-10 gene was found on ten of the twelve chromosomes, and it was determined through a genetic ontology that they were involved in six biological processes and molecular activities, and nine cellular components. Analysis of the transcription level of PR-10 family members showed that the PR-10 gene (Solyc09g090980) has high expression levels in some parts of the tomato plant. PR-10 and Sw-5b gene transcription and activity in tomato leaves were strongly induced by TSWV infection, whereas H8 plants having the highest significantly upregulated expression of PR-10 and Sw-5b gene after the inoculation of TSWV, and TSWV inoculated in M82 plants showed significantly upregulated expression of PR-10 gene comparatively lower than H8 plants. There was no significant expression of Sw-5b gene of TSWV inoculated in M82 plants and then showed highly significant correlations between PR-10 and Sw-5b genes at different time points in H8 plants showed significant correlations compared to M82 plants after the inoculation of TSWV; a heat map showed that these two genes may also participate in regulating the defense response after the inoculation of TSWV in tomato.

Identification and Characterization of Plant-Interacting Targets of Tomato Spotted Wilt Virus Silencing Suppressor.

Tomato spotted wilt virus (TSWV; species Tomato spotted wilt orthotospovirus) is an economically important plant virus that infects multiple horticultural crops on a global scale. TSWV encodes a non-structural protein NSs that acts as a suppressor of host RNA silencing machinery during infection. Despite extensive structural and functional analyses having been carried out on TSWV NSs, its protein-interacting targets in host plants are still largely unknown. Here, we systemically investigated NSs-interacting proteins in Nicotiana benthamiana via affinity purification and mass spectrometry (AP-MS) analysis. Forty-three TSWV NSs-interacting candidates were identified in N. benthamiana. Gene Ontology (GO) and protein–protein interaction (PPI) network analyses were carried out on their closest homologs in tobacco (Nicotiana tabacum), tomatoes (Solanum lycopersicum) and Arabidopsis (Arabidopsis thaliana). The results showed that NSs preferentially interacts with plant defense-related proteins such as calmodulin (CaM), importin, carbonic anhydrase and two heat shock proteins (HSPs): HSP70 and HSP90. As two major nodes in the PPI network, CaM and importin subunit α were selected for the further verification of their interactions with NSs via yeast two-hybrid (Y2H) screening. Our work suggests that the downstream signaling, transportation and/or metabolic pathways of host-NSs-interacting proteins may play critical roles in NSs-facilitated TSWV infection.

First report of tomato spotted wilt virus (TSWV) isolated from nasturtium (Tropaeolum majus L.) with a serious leaf mosaic disease in China.

Tomato spotted wilt virus (TSWV, Genus Orthotospovirus, Family Tospoviridae) is a thrips-transmitted negative-stranded RNA virus with a large host range. Major economic losses caused by TSWV have been recorded in various crops such as tomato, pepper and lettuce (Pappu et al., 2009; Adams et al., 2017). Nasturtium (Tropaeolum majus L.), acommon flowering plant speciesnative to Peru, is generally cultivated as a garden and greenhouse ornamental plant in China. It is also known for its medical, edible and cosmetic values (Jakubczyk et al., 2018). In June 2019, a serious leaf mosaic disease (Figure S1) was observed in ~77% of T. majus plants in Beiling Park in Shenyang City, Liaoning, China. To reveal the possible viral agent associated with the disease, leaf tissue was collected from 9 symptomatic and 2 asymptomatic plants, followed by total RNA extraction from each of the samples using RNASimple Total RNA Kit (Tiangen, Beijing, China). The RNA from one representative symptomatic sample (Figure S1, d) was used to construct an rRNA-depleted library using the Ribo-Zero™ rRNA Removal Kit (Plant Leaf) (Illumina, CA, USA). The library was subjected to RNA-Seq using a BGISEQ platform (Shenzhen Huada Gene Science and Technology Service Co., Ltd., Shenzhen, China). A total of 109,279,540 quality-filtered reads were obtained using the CLC Genomics Workbench 9.5 software (Qiagen, Valencia, CA, USA). Clean reads were assembled into 88,091 contigs ranging in length from 200 to 19,695 bp using Velvet (Zerbino and Birney 2008). Among the contigs, three sized at 8801, 4617 and 2909 bp were found to share a sequence identity of 98.74-99.35% with the RNA segments (L, M and S) of TSWV. No sequences of other viruses, viroids included, were detected. Ten primer pairs were designed based on the TSWV contigs to obtain the full genome sequence of the virus (Table S1). Five, three, and two amplicons were obtained for the TSWV RNA segments L, M and S, respectively, from the same RNA sample used in the RNA-Seq process. These amplicons were then cloned into the pMD18T vector (TaKaRa, Dalian, China) and Sanger sequenced. The resulting sequences were assembled and analyzed using the DNAMAN version 8.0 (LynnonBiosoft, Quebec, Canada) and DNAStar version 6.0 software (DNAStar Inc, Madison, WI, USA) (Table S1). The RNA segments were determined to be 8,914 nt (L, accession no. MT241883), 4,791 nt (M, MT241884) and 2,922 nt (S, MT241885) in length. They shared a sequence identity of >99% with the "LL-N.05" (segment L, KP008128) and "SPAIN-1" (segment S, AY744479) isolates from tomatoes in Spain and the "Beijing" isolate (segment M, MH717046) from chrysanthemum in China. These results, together with phylogenetic analysis, suggest that the isolate (designated as isolate LN-HJL) was likely resulted from genome reassortment between other isolates. No reliable recombination events were detected in the RNA segments of LN-HJL by the RDP4 program (Martin et al., 2015). RT-PCR assay with primer pair S-1F/1R on all samples led to positive detection of TSWV only in the symptomatic samples (Figure S1, g), indicating that the virus was likely responsible for the disease symptoms observed in T. majus. To the best of our knowledge, this is the first report of the TSWV infection in T. majus in China, and the second in the world since the first report in the USA (Ie, 1964). TSWV-infected T. majus plants not only lose their aesthetic and economic values (Figure S1, f), but also may act as reservoirs for the spread of TSWV to other important crops. T. majus should therefore be monitored regularly for the virus and managed accordingly in China.

Development of an IPM Strategy for Thrips and Tomato spotted wilt virus in Processing Tomatoes in the Central Valley of California.

Tomato spotted wilt virus (TSWV; species Tomato spotted wilt orthotospovirus; genus Orthotospovirus; family Tospoviridae) is a thrips-transmitted virus that can cause substantial economic losses to many crops, including tomato (Solanum lycopersicum). Since 2005, TSWV emerged as an economically important virus of processing tomatoes in the Central Valley of California, in part due to increased populations of the primary thrips vector, western flower thrips (WFT; Frankliniella occidentalis). To develop an understanding of the epidemiology of TSWV in this region, population densities of WFT and incidence of TSWV were monitored in California’s processing tomato transplant-producing greenhouses and associated open fields from 2007 to 2013. Thrips were monitored with yellow sticky cards and in tomato flowers, whereas TSWV incidence was assessed with indicator plants and field surveys for virus symptoms. All thrips identified from processing tomato fields were WFT, and females were three-fold more abundant on sticky cards than males. Symptoms of TSWV infection were observed in all monitored processing tomato fields. Incidences of TSWV ranged from 1 to 20%, with highest incidence found in late-planted fields. There was no single primary inoculum source, and inoculum sources for thrips/TSWV varied depending on the production region. These results allowed us to develop a model for TSWV infection of processing tomatoes in the Central Valley of California. The model predicts that low levels of primary TSWV inoculum are amplified in early-planted tomatoes and other susceptible crops leading to highest levels of infection in later-planted fields, especially those with high thrips populations. Based upon these findings, an integrated pest management (IPM) strategy for TSWV in processing tomatoes in California was devised. This IPM strategy focuses on strategic field placement (identification of high-risk situations), planting TSWV- and thrips-free transplants, planting resistant varieties, monitoring for TSWV symptoms and thrips, roguing infected plants, thrips management targeting early generations, extensive sanitation after harvest, and strategic cropping to avoid overlap with winter bridge crops.

Bacillus amyloliquefaciens strain MBI600 induces salicylic acid dependent resistance in tomato plants against Tomato spotted wilt virus and Potato virus Y

Plant growth promoting rhizobacteria have been proposed as effective biocontrol agents against several fungal and bacterial plant pathogens. However, there is limited knowledge regarding their effect against viruses. In this study, Bacillus amyloliquefaciens strain MBI600 (MBI600), active ingredient of the biological fungicide Serifel® (BASF SE), was tested for its antiviral action in tomato plants. Drench, foliar or soil amendment applications of MBI600 reduced up to 80% the incidence of Tomato spotted wilt virus under two different sets of environmental conditions. In addition, drench application of MBI600 delayed Potato virus Y systemic accumulation. Transcriptional analysis of a range of genes associated with salicylic acid (SA)- or jasmonic acid - related defense, priming or basal defense against viruses, revealed the induction of the SA signaling pathway in tomato after MBI600 treatment, and discrete gene expression patterns in plant response to TSWV and PVY infection.

Effects of Thrips Density, Mode of Inoculation, and Plant Age on Tomato Spotted Wilt Virus Transmission in Peanut Plants.

Spotted wilt caused by tomato spotted wilt virus (TSWV; family Bunyaviridae; genus Tospovirus) is a serious disease of peanut (Arachis hypogaea L.) in the southeastern United States. Peanut genotypes with field resistance to TSWV are effective in suppressing spotted wilt. All commercially available genotypes with field resistance to TSWV were developed through conventional breeding. As a part of the breeding process, peanut genotypes are regularly screened under field situations. Despite numerous advantages associated with field screening, it is often limited by inconsistent vector (thrips) and TSWV pressure. A greenhouse transmission protocol would aid in thorough screening of selected genotypes and conserve time. In this study, various parameters associated with TSWV transmission, including tobacco thrips, Frankliniella fusca (Hinds) density, mode of inoculation, and plant age, were evaluated. Greater incidences of TSWV infection were obtained with thrips-mediated inoculation when compared with mechanical inoculation. TSWV inoculation with three, five, and 10 thrips resulted in greater incidences of TSWV infection in plants than inoculation with one thrips. However, incidences of TSWV infection did not vary between plants inoculated with three, five, and 10 viruliferous thrips. With both thrips-mediated and mechanical inoculation methods, incidences of TSWV infection in 1-wk-old plants were greater than in 4-wk-old plants. TSWV copy numbers, as determined by qPCR, also decreased with plant age. Results suggest that using at least three thrips per plant and 1- to 2-wk-old plants would maximize TSWV infection in inoculated plants.

First outbreak of Chrysanthemum stem necrosis virus (CSNV) on potted Chrysanthemum in Belgium

In Belgium, potted Chrysanthemum x morifolium cultivation covers about 400 ha, of which 375 ha is in open fields and the remaining portion in glasshouses. This represents nearly half of total European production. Among the most important pests and diseases with a significant impact on chrysanthemum production are the western flower thrips (Frankliniella occidentalis) and spotted wilt (Tomato spotted wilt virus TSWV), for which the thrips acts as a vector. So far, Chrysanthemum stem necrosis virus (CSNV), a distinct member of the genus Tospovirus (Bezerra et al., 1), has only been described in a limited host range and with a restricted geographical distribution. However, even with limited data available on losses caused by CSNV in its major areas of distribution i.e. Brazil and Japan, the phytosanitary risk to chrysanthemum and tomato crops, in areas where its vector F. occidentalis is known to occur, is considered high. Moreover, while symptoms of CSNV and TSWV are comparable, CSNV-induced disease often develops faster and is more destructive (Bezerra et al., 1). In October 2012, plants suspected to be virus-infected in showing wilting and having numerous necrotic lesions surrounded by yellow areas, were received from a seasonal chrysanthemum grower, growing under glass in western Belgium. Initially TSWV infection was suspected but the necrotic zones quickly extended to stems (Fig. 1), ultimately killing most of the crop in the case of cvs. Ludo and Jorca Pink (Fig. 2). Losses for the cv. Mirage Yellow (Fig. 3) also grew to more than 50%. Cultivar Miral White and an assorted cultivar mix were also infected, although symptoms remained less severe. Cuttings from all of these cultivars originated from Brazil. After an initial screen for TSWV with TSWV reagent set (Art. No. 190165, BIOREBA, Switzerland), followed by a CSNV test (AS-0529; DSMZ, Germany), both by DAS-ELISA, further detection and identification of the virus by PCR was based on the nucleocapsid (N) gene sequence. Total RNA was extracted from leaf and stem tissue using a Spectrum Total Plant RNA kit (Sigma-Aldrich, Belgium). The specific CSNV-N5/N3 PCR primers developed by Takeshita et al. (5) were used to amplify the N gene ORF (approx. 950 bp) and these fragments were cloned (Clonejet PCR cloning kit, Thermo Scientific, Belgium) and sequenced. CSNV infection was confirmed on all sampled plants with symptoms from all five infected cultivars, and no variability was noticed in their respective N gene sequences. The consensus 937 bp sequence of the N gene is available from GenBank (Accession No. KC525102). Symptomless plants did not test positive for CSNV nor any other tospoviruses. Infected plant material from the cv. Ludo was mechanically inoculated on a series of indicator plants and resulted in symptoms corresponding to those described by Bezerra et al. (1). RT-PCR on symptomatic indicator plants again confirmed the presence of CSNV. This is the first report of a CSNV outbreak in Europe in 10 years. Previous outbreaks in the Netherlands (Verhoeven et al., 2003), Slovenia (Ravnikar et al., 4) and UK (Mumford et al., 3) were all declared eradicated (EPPO, 2). The infected production facility is now under eradication measures and the virus will remain subject to official control in 2013.

Oxylipin Biosynthesis Genes Positively Regulate Programmed Cell Death during Compatible Infections with the Synergistic Pair Potato Virus X-Potato Virus Y and Tomato Spotted Wilt Virus

One of the most severe symptoms caused by compatible plant-virus interactions is systemic necrosis, which shares common attributes with the hypersensitive response to incompatible pathogens. Although several studies have identified viral symptom determinants responsible for systemic necrosis, mechanistic models of how they contribute to necrosis in infected plants remain scarce. Here, we examined the involvement of different branches of the oxylipin biosynthesis pathway in the systemic necrosis response caused either by the synergistic interaction of Potato virus X with Potato virus Y (PVX-PVY) or by Tomato spotted wilt virus (TSWV) in Nicotiana benthamiana. Silencing either 9-lipoxygenase (LOX), 13-LOX, or α-dioxygenase-1 (α-DOX-1) attenuated the programmed cell death (PCD)-associated symptoms caused by infection with either PVX-PVY or TSWV. In contrast, silencing of the jasmonic acid perception gene, COI1 (Coronatine insensitive 1), expedited cell death during infection with compatible viruses. This correlated with an enhanced expression of oxylipin biosynthesis genes and dioxygenase activity in PVX-PVY-infected plants. Moreover, the Arabidopsis thaliana double lox1 α-dox-1 mutant became less susceptible to TSWV infection. We conclude that oxylipin metabolism is a critical component that positively regulates the process of PCD during compatible plant-virus interactions but does not play a role in restraining virus accumulation in planta.

First report of Tomato spotted wilt virus on tomato in Syria.

During spring and early summer of 2007 and 2008, a survey was carried out to investigate the presence of Tomato spotted wilt virus (TSWV, genus Tospovirus, family Bunyaviridae) in 643 tomato samples (leaves and fruits) from grower fields (422 sam- ples from 68 fields) and five Agricultural Research Stations of GCSAR (221 samples), representing eight Syrian governorates. Samples were tested by DAS-ELISA (Clark and Adams, 1977) using a commercial kit (Bioreba, Switzerland). An overall 11% infection rate (72 of 643 samples) was found, the highest being in the governorate of Al-Qunaitara (41%), followed by Dar’a (22%), Damascus countryside (12%), Aleppo (3%) and Idleb (2%). No TSWV infection was recorded in any of the Agricultur- al Research Stations inspected and in governorates of Homs, Hama and Tartous. The presence of TSWV was confirmed by one-step RT-PCR analysis of a few selected samples using the Ac- cess System (Promega, USA), total RNA extracted with TRIzol LS (Invitrogen, USA) and primer pair 722/723 designed in the vi- ral nucleocapsid protein (NP) gene (Adkins and Rosskopf, 2002). The expected 620 bp DNA fragment was obtained from seven samples (four from Dar’a and three from Damascus countryside), as shown by electrophoresis on 1% agarose gel. To our knowl- edge, this is the first record of TSWV on tomato in Syria.

Potatovirus X and Tobacco mosaic virus-based vectors compatible with the Gateway™ cloning system

Virus-based expression vectors are important tools for high-level production of foreign proteins and for gene function analysis through virus induced gene silencing. To exploit further their advantages as fast, high yield replicons, a set of vectors was produced by converting and adapting Potato virus X (PVX) and Tobacco mosaic virus (TMV)-based vectors to allow easy cloning of foreign sequences by the Gateway™ cloning system. Target genes were cloned efficiently by recombination and successfully expressed in Nicotiana benthamiana following inoculation by Agrobacterium (agroinfection). Using green fluorescent protein (GFP) as marker, high-level expression with both PVX-GW and TMV-GW vectors was confirmed. A Gateway inserted phytoene desaturase gene ( pds) fragment in PVX-GW and TMV-GW vectors (PVX-GW-PDS and TMC-GW-PDS), induced gene silencing of the endogenous pds gene in N. benthamiana as evidenced by chlorotic leaves. The PVX-GW vector was adapted further by cloning the GFP gene upstream of the Gateway sequences, allowing the easy production of GFP fusions after recombination of a target gene. Subcellular localization of resulting GFP fusion was validated by recombining and expressing the coat protein gene from Tomato chlorotic mottle virus, revealing its nuclear localization. A PVX-GW transient expression assay of a nucleocapsid protein gene fragment of Tomato spotted wilt virus and of a single chain antibody against this protein was shown to confer effective resistance to TSWV infection.

First Report of Tomato spotted wilt virus Infecting African Clover (Trifolium tembense) in Georgia.

Tomato spotted wilt virus (TSWV; family Bunyaviridae, genus Tospovirus), which is vectored by several species of thrips (order Thysanoptera, family Thripidae), causes a destructive disease that affects many economically important host plants such as tomatoes, peppers, and peanuts. Controlling the spread of this disease is challenging, and currently, only limited strategies are available to prevent and/or control its dissemination, including early diagnosis, destruction of infected material, and elimination of the vector. TSWV has been previously reported in subterranean clover (Trifolium subterraneum), white clover (T. repens), and various unidentified wild clovers (Trifolium spp.) in North America and Australia (1,3), but never before in an African species. T. tembense (Fresen.), an herbaceous annual African clover that is mainly used for grazing, is part of the national germplasm collection housed at the Plant Genetic Resources Conservation Unit in Griffin, GA. TSWV was found naturally infecting several accessions of this species being grown for regeneration in a greenhouse during 2008. Initial putative identification of the virus was done by visual inspection of host symptoms that included ringspots, necrotic and chlorotic local lesions, sometimes mild systemic wilting, and eventually an overall decline of healthy tissue in the infected plants. This was subsequently confirmed by double-antibody sandwich (DAS)-ELISA and reverse transcription (RT)-PCR. Primers (5'-ATGTCTAAGGTTAAGCTC-3' forward and 5'-TTAAGCAAGTTCTGTGAG-3' reverse) targeted the nucleocapsid gene of TSWV and amplified an expected product of approximately 800 bp (2). No product was amplified in any of the negative controls. Twenty-six individuals representing twelve plant accessions (PI 517788, 517790, 517792, 517793, 517809, 517832, 517842, 517845, 517851, 517871, 517876, and 517889) were screened for TSWV. Two to three individuals were targeted from each accession. Samples were chosen on the basis of the availability of leaf tissue to perform two diagnostic assays, ELISA and RT-PCR. Samples chosen for this study were all naturally infected by thrips. All but four individuals representing two plant accessions tested positive for the virus. The RT-PCR data substantiated the DAS-ELISA results and confirmed the suspected infection. More than 26% of the positive samples naturally infected by TSWV were further characterized by purifying and sequencing (bidirectionally) the RT-PCR product on an automated CEQ 8000 sequencer (Beckman Coulter, Fullerton, CA). The resulting sequences were aligned and edited using AlignIR (LI-COR, Lincoln, NE). More than 700 bp of sequence data (GenBank Accession No. FJ183743-FJ183746) was compiled and they displayed 98% identity with deposited TSWV nucleocapsid gene sequences in GenBank, with no similarity to any other targets. To our knowledge, this is the first report of TSWV infection in T. tembense. Accessions potentially resistant to TSWV within this species were identified and need to be further substantiated. T. tembense is a wild, native clover in Africa and could serve as a weed host for infection of nearby agronomically important crops.

Variation Among Virginia Market-Type Peanut Genotypes in Susceptibility to Tomato Spotted Wilt Virus Vectored by Thrips (Thysanoptera: Thripidae)

Abstract Tomato spotted wilt virus (TSWV), a thrips-vectored tospovirus, is an important pathogen of peanut (Arachis hypogaea L.). Development of tolerant cultivars has proven to be one of the most promising methods to manage the disease. Twenty-four genotypes of virginia market-type peanut were monitored in field tests for thrips damage, and TSWV incidence and severity during 2004 and 2005 in North Carolina. The cultivar Gregory had a higher density of adult thrips in foliage than any other genotype, while breeding lines N01057 and N03054E had the lowest density. No significant correlation was detected between thrips density or injury and TSWV incidence. Line N03036EJ had the greatest TSWV incidence, but did not differ from cultivars Gregory or Perry in incidence. Line N00033 had the least TSWV incidence and differed from the cultivars Gregory and Perry. The occurrence of late-season chlorosis or peanut yellowing death (PYD) was highly correlated with TSWV infection (P < 0.0001). Breeding line N02051ol had the greatest incidence of PYD, but did not differ statistically from Gregory or Perry. Lines N03023EF and N01083 had the least PYD incidence. Plants infected with TSWV not expressing foliar symptoms were found in far greater abundance than plants that were infected and symptomatic. Line N03036EJ had the greatest proportion of infected but asymptomatic plants; line N03054E had the least. Susceptible lines are more likely to become infected, rather than just more likely to show spotted wilt symptoms.

Effect of Tomato Spotted Wilt Tospovirus (TSWV) Infection on the Fruits of Tomato (Lycopersicon esculentum) Plants of Cultivars Carrying the SW‐5 gene

Peculiar necrotic ring spots on tomato fruits from TSWV‐resistant plants containing SW‐5 gene that occur in field conditions are caused by feeding of viruliferous thrips as shown by transmission assays conducted in controlled conditions. The ring spots are caused by a progressive TSWV infection probably due to insufficient hypersensitive response as a consequence of the presence of the SW‐5 gene. These diseased fruits appeared 5 weeks later than typical symptoms of TSWV infection on leaves of susceptible plants in a comparative study performed in an early‐transplanted tomato field. The percentage of susceptible tomato hybrids infected by TSWV was approximately 14%, whereas only 4% of symptom‐free plants of TSWV‐resistant hybrids showed some diseased fruits. Only 11% of the fruits of these plants were infected. These results could change depending on the feeding behaviour and the proportion of viruliferous thrips in the thrips population during the early stages of fruit development. Changes in management practices in tomato crops conducted to reduce their populations at this time of the season could decrease the number of unmarketable fruits. The presence of TSWV‐resistant plants showing a systemic infection in open commercial tomato fields with higher proportions than expected is discussed.

First Report of Tomato spotted wilt virus in Common Agapanthus.

Common agapanthus (Agapanthus praecox subsp. orientalis), native to South Africa, is a popular ornamental flowering bulb species belonging to the Amaryllidaceae and is commonly found in residential gardens. Roots from some Agapanthus sp. also are used in traditional medicine in Africa. Common agapanthus collected from a residential property in Hobart, Tasmania, Australia, showed leaf symptoms of concentric ring and line patterns, irregular chlorotic blotches, and streaks. Symptomatic plants were severely stunted and failed to flower. Symptomatic leaves prematurely senesced, but young foliage subsequently produced was symptomless. Similar symptoms have been reported in other members of the Amaryllidaceae and are associated with infection by Tomato spotted wilt virus (TSWV; e.g., Nerine and Hippeastrum spp.) or Cucumber mosaic virus (CMV; e.g., Hippeastrum sp.) (2). The presence of TSWV and absence of CMV in symptomatic plants of common agapanthus was determined by enzyme-linked immunosorbent assay. Confirmation of TSWV infection was provided by reverse-transcription polymerase chain reaction assay with primers specific to the nucleocapsid protein gene of TSWV, with nucleic extracts from symptomatic plants producing an expected ≈800-bp amplicon (1). This is the first report of TSWV infection of any species within the Amaryllidaceae in Australia and the first report of the occurrence of TSWV in common agapanthus.

Localization of Tomato Spotted Wilt Virus (Genus Tospovirus, Family Bunyaviridae) in Peanut Pods

Abstract The localization of tomato spotted wilt virus (TSWV, genus Tospovirus, family Bunyaviridae) in peanut pods was determined by enzyme-linked immunosorbent assay (ELISA) using TSWV specific antibodies. Pods were collected from symptomatic and asymptomatic fieldgrown plants. All the plants were tested by ELISA for presence or absence of TSWV infection. Normal and abnormal looking pods from symptomatic plants were assayed by ELISA. Each pod was divided into shell, testa, and cotyledons. All of the shell and testa samples of both normal and abnormal pods from symptomatic plants were positive for TSWV, whereas TSWV could not be detected in the cotyledons. Similar results were observed by polymerase chain reaction, except that the cotyledons occasionally had a TSWV-specific sequence. No virus could be detected in any part of the pod collected from asymptomatic, virus-free plants. In growout tests of seed from both symptomatic and asymptomatic plants, none of the plants showed TSWV infection when assayed by ELISA. Results demonstrated the preferential accumulation of the virus in the shell and testa.